supplementary materials

In the title hydroxamic acid derivate, C21H14N2O5Cl2, the nitro-substituted benzene ring forms dihedral angles of 66.0 (2) and 59.6 (2)°, with the p-chloro and o-chloro-substituted benzene rings, respectively. The dihedral angle between the two chloro-substituted benzene rings is 64.2 (2) Å. In the crystal, weak C-HO hydrogen bonds link the molecules along [010]. The crystal studied was an inversion twin with refined components in the ratio 0.60 (7):0.40 (7).

Hydroxamic acid derivatives have received considerable attention in recent years
as the result of the discovery of their role in the biochemical toxicology of
many drugs and other chemicals (Noh et al., 2009; Zeng et
al.,
2003). The molecular structure of the title compound is sjown in Fig.
1. The
nitro-substituted benzene ring (C16-C24) forms dihedral angles of 66.0 (2) and
59.6 (2)°, with the 4-chloro (C1-C6) and 2-chloro-substituted (C8-C13) benzene
rings, respectively. The dihedral angle between the two chloro-substituted
benzene rings (C1-6/C8-C13) is 64.2 (2)Å. In the crystal, weak C—H···O
hydrogen bonds linke molecules along [010] (Fig .2).
The bond legths and angles can be compared to those in
N-(2-Chlorophenyl)-1-phenylformamido 3-(2-nitrophenyl)propanoate
(Zhang et al., 2012).

The title compound (I) was prepared according to the
method described by Ayyangark et al. (1986). Crystals suitable
for
single-crystal X-ray analysis were grown by slow evaporation of a
solution of (I) in dichloromethane-methanol (1:3 v/v).

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger.